The metalwork is done, but I'm not sure about the pulley. The bearings it fits onto are 22mm OD, and the overall diameter of the pulley is 35mm (because that happens to be the size of nylon rod that I have lying around). The thickness is 17mm and the chain runs in a groove 10mm wide by 4.5mm deep.
Do folks reckon this shape would work okay, or might the chain have a tendency to slip off? I've designed the spindle so that there is scope to adjust the left/right position of the pulley to try and keep the chain path central.
I'm not sure it'll work on either side, I rekon the groove is just too shallow, for reference the drive side idler on the catrike is 65mm dia with a groove that's 12mm deep and tapers from 10mm to 8mm wide. I think it's got an O-ring at the bottom as well to keep it lovely and quiet.
I think it's got an O-ring at the bottom as well to keep it lovely and quiet.
On the Speed Ross, with idler from who knows where, I find a piece of old inner tube cut to the inner width of the pulley, and replaced about every 3 months when the oil on the chain rots through it, works.
Iv'e a similar arrangement on my Windcheetah. Works well, except the chain can jump off on fast rough roads. The answer is a bolt going through the brackets and across the outside of the chain. Of course it normally takes no load at all.
If you are looking at the idling side then the Windcheetah gets by with just a nylon block with a hole machined in it for the chain to slide through.
Regards
Rod
"Wally" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
I'm making a chain idler for my recumbent build. 3D CAD-piccy here...
The metalwork is done, but I'm not sure about the pulley. The bearings it fits onto are 22mm OD, and the overall diameter of the pulley is 35mm (because that happens to be the size of nylon rod that I have lying
around).
Quoted message said:
The thickness is 17mm and the chain runs in a groove 10mm wide by 4.5mm deep.
Do folks reckon this shape would work okay, or might the chain have a tendency to slip off? I've designed the spindle so that there is scope to adjust the left/right position of the pulley to try and keep the chain
Iv'e a similar arrangement on my Windcheetah. Works well, except the chain can jump off on fast rough roads. The answer is a bolt going through the brackets and across the outside of the chain. Of course it normally takes no load at all.
If you are looking at the idling side then the Windcheetah gets by with just a nylon block with a hole machined in it for the chain to slide through.
Regards
Rod
I wouldn't model you chain mangement on the Windcheetah, not the return side at least beacuse it's rubbish (sorry, I've got one too!). A return chain tube would have been much better and would have stopped the chain swinging about, slapping into the main tube, been a lot quieter, not get jammed over bumps and not sometimes de-rail at the front if you go over a bump and aren't pedalling.
I'm not sure it'll work on either side, I rekon the groove is just too shallow, for reference the drive side idler on the catrike is 65mm dia with a groove that's 12mm deep and tapers from 10mm to 8mm wide. I think it's got an O-ring at the bottom as well to keep it lovely and quiet.
The bracket I have will take 60mm, so I think I'll track down some bigger pulley material.
"Alexander Rice" <[email hidden]> wrote in message news:[email hidden]...
Quoted message said:
I wouldn't model you chain mangement on the Windcheetah, not the return side at least beacuse it's rubbish (sorry, I've got one too!). A return chain tube would have been much better and would have stopped the chain swinging about, slapping into the main tube, been a lot quieter, not get jammed over bumps and not sometimes de-rail at the front if you go over a bump and aren't pedalling.
Alex
I am not sure how a return chain tube would be much better as it would still need to take in the angles. Presumably it would have to be fixed near the front idler wheel. I have never had the chain jam over bumps and the occassional de-rail is when going downhill is over bumps when the simple solution is just to change gear back onto the front chainwheel.
However, I have no experience of chain tubes. If you do fit one please let me know how you get on with it.
On the Speed Ross, with idler from who knows where, I find a piece of old inner tube cut to the inner width of the pulley, and replaced about every 3 months when the oil on the chain rots through it, works.
The bearings are reputed to be for skateboards and roller blades - 20mm OD,
Typo: 22mm OD.
The other trick I've seen employed with the skateboard wheel is to turn two groves in the wheel, one for the power route of the chain (nearer the frame), and one for the return path. The wheel has to be rotated by the power path, so might as well go round and help the return path along its way.
If you are going to try the skateboard wheel route, make sure that you get the ones that are the same material all the way through - some have a 4-5mm coating which you cut through when turning the groove rendering them pretty useless.
